1. Field of Invention
The present invention is a cable with a predetermined shape that allows two members to rotate relative to each other.
2. Description of Related Art
Robots typically have at least one degree of freedom that allows relative rotational movement between two rigid structures. The structure that is in motion usually has an actuator or electric motor at one end to grasp, weld or perform other types of functions. The actuator or motor is connected by wires to a source of electric power. The wire is usually attached to the robot such that it must pass through a joint between the two structures. To allow the wire to move with the rotating structure, the wire is provided with additional length or slack, so that the wire can extend when the rotating structure is rotated into its maximum extension. The extra wire length dangles about and is susceptible to entanglement with the rotating structure. Because the wire typically extends through the joint, the wire can also become pinched and severed by the rotation of the structure. Rotating electrical couplings such as slip rings can be used, but these are subject to wear and contamination and can create an undesirable amount of electrical resistance in the line, particularly when power or signals must pass over multiple joints in series.
Therefore what is needed is a wire configuration that allows relative rotational movement between two structures without having to provide excess wire length that can become entangled, pinched, or produce an excessive amount of electrical resistance.